The present invention relates to a hydraulic pressure actuating apparatus for a circuit breaker, and in particular, to a hydraulic pressure actuating apparatus being suitable for use in a circuit breaker for use in electric power supply.
With the conventional circuit breaker, as was described in Japanese Patent Laying-open No. Hei 7-217401 (1995), for example, a hydraulic device for a high-tension circuit breaker has an actuating piston for use in a traveling or moving contact point thereof. The traveling contact point has two (2) pieces of pistons connected to a high-pressure tank under the closing condition, and those two (2) pistons are driven by high-pressure liquid acting thereon. In circuit breaking, a directional control valve operates so that a flow passage is formed at a low-pressure side of the piston. Pilot valves for closing and pilot valves for cutting-off actuate the directional control valve. And, the two (2) pieces of the pilot valves for use in circuit cutting-off are connected to the directional control valve.
In the circuit breaker described in the Japanese Patent Laying-Open No. Hei 7-217401 (1995) mentioned above, when one of the pilot valves will not operated since something abnormal occurs therein, then only the other pilot valve actuates, thereby causing a drawback that the time is changed, being necessary for making contacts open and close in the circuit breaker. With the circuit breaker for use in electric power supply, the time necessary for the circuit breaker to open the contacts thereof (i.e., a time period from an open-circuit instruction up to the time when the contact point is opened), as well as, the time to close the contacts (i.e., a time period from a close-circuit instruction up to the time when the contact point is contact with) must be within a predetermined range of time. Also, if the circuit breakers are provided for each of the phases, it is necessary that the difference in operation time is small between those phases. Further, it is also desired to make the circuit breaker small-sized by reducing the numbers of bodies, in which the valves are inserted, and/or conduits formed, as well as, to reduce the cost thereof.
An object of the present invention, for dissolving the drawback of the conventional arts mentioned above, is to provide a hydraulic pressure actuating apparatus for a circuit breaker, with which reliability of the circuit breaker can be improved. Other object, according to the present invention, is to provide a hydraulic pressure actuating apparatus for a circuit breaker, with which the actuating time of the circuit breaker can be kept constant for a long time. And further other object, according to the present invention, is to provide hydraulic pressure actuating apparatus for a circuit breaker, which can be made small in sizes thereof, thereby reducing the cost thereof.
For accomplishing the object mentioned above, according to the present invention, there is provided a hydraulic pressure actuating apparatus for a circuit breaker, for opening/closing a contact point having a moving contact and a stationary contact by actuating a piston received within a cylinder, comprising: a directional control valve for exchanging pressure for actuating said piston; and a circuit-close pilot valve and an circuit-open pilot valve for making a flow passage open/close, being connected to said directional control valve, wherein in each of said pilot valves, two (2) pieces of valve bodies are positioned opposing to each other, and movable directions of said valve bodies are directed substantially opposite to each other.
Further, according to the present invention, in the hydraulic pressure actuating apparatus for a circuit breaker, as described in the above, wherein preferably, said valve bodies are disposed, so that they are in contact with each other, when one of said valve bodies is changed in position up to maximum stroke while the other valve body is changed in position at minimum stroke, or the maximum strokes of said valve bodies are made almost equal to each other. And, further, it is preferable that flow passage area of the pilot valve changes in proportion with a stroke of said valve body, or a spring is connected between said valve bodies.